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Research Watch Report: Attention and Memory in Adults with TBI

Research Watch Report: Attention and Memory in Adults with TBI
April Garrity, PhD, CCC-SLP
June 21, 2018
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Introduction

Attention may be defined as “the flexible allocation of cognitive resources toward stimuli, internal representations, and outputs that are currently most important for the accomplishment of a behavioral goal” (Dosenbach & Peterson, 2009). The word “attention” might be used to describe a spectrum of functions, from basic arousal or awareness to more complex forms of attention that require the individual to focus on specific stimuli (focused attention), maintain focus on specific stimuli (sustained attention), and attend to more than one stimulus, including ignoring irrelevant information (divided attention) (Davis, 2014).

Memory, like attention, is used to describe a number of different ways of storing and retrieving information. Working memory refers to short-term storage of information as well as the ability to manipulate the information, or “work” with it, possibly while accessing the various forms of long-term memory. For example, an example of a working memory task would be giving a client a list of three words and asking them to remember and repeat those words back to you, but to first put them in alphabetical order. Long-term memory is comprised of declarative and non-declarative memory. The difference between declarative and non-declarative memory is in the conscious awareness of it. Declarative memory includes storage of events (episodic memory), facts and concepts (semantic memory), and the ability to remember something that will happen in the future (prospective memory). These are memories that have been consciously stored through explicit learning. Non-declarative memory, on the other hand, includes memory for how to carry out tasks like tying one’s shoes or riding a bike (procedural memory) as well as associating certain feelings with specific people or experiences (emotional associations). These memories are formed without specific conscious awareness of the procedures or feelings (Sohlberg & Turkstra, 2011).

SLPs assess and treat attention and memory impairments, as well as other cognitive deficits, as part of our practice with individuals with cognitive communication disorders. Individuals who have sustained a brain injury often exhibit deficits in these areas that often significantly interfere with their functional independence in activities of daily living, relationships, and academic or vocational pursuits. This Research Brief will focus on some of the most current research in the areas of attention and memory impairments in adults with TBI. The articles summarized here are drawn from a journal specific to speech-language pathology as well as from those in related disciplines, and, as such, may reference modalities or platforms not traditionally utilized in the provision of speech-language pathology services. However, we as SLPs can benefit from these other avenues of research in order to gain a broader understanding of the evidence base to inform our practice with clients with TBI.

Characterizing Attention and Memory Skills in Individuals with TBI

Article 1: Robertson, K., & Schmitter-Edgecombe, M. (2017). Focused and divided attention abilities in the acute phase of recovery from moderate to severe traumatic brain injury. Brain Injury, 31(8), 1069-1076.

Background: Why was this study conducted? Both focused and divided attention have various functional applications. The authors of this study gave an example of how one would need to utilize one or the other of these types of attention when looking for a friend in a crowded room. Divided attention would be required if you need to search the entire room for your friend because you aren’t sure where exactly he or she is in the room. This scenario would require you to both search for a specific target, while simultaneously ignoring irrelevant information, i.e., people or objects that are not your friend. Focused attention, on the other hand, would apply if, for example, you knew that your friend were in a particular area of the crowded room, i.e., by the piano.

These types of attention are typically considered to be impaired among individuals with TBI. However, the authors suggest that the tasks used to study these different constructs might not actually be valid measurements of both types of attention. They argue that the tasks might well be confounded by cognitive artifacts like general processing speed. The goal of this study was to use an experimental task that would yield higher validity for measures of focused and divided attention among individuals in the early stages of TBI. The authors wanted to answer these questions: (1) How does the performance of participants in the acute phase of TBI compare to participants without TBI on tasks of focused and divided attention? (2) Do participants with TBI make use of location cues and ignore distracting stimuli on these tasks?

Method: Who participated in the study and what did they do? Participants in the study included 30 participants with TBI (20 males, 10 females) and 30 control participants. The controls were matched to the participants with TBI on several variables, including age, education, gender, and estimates of premorbid intelligence. All participants with TBI had sustained a closed head injury resulting in moderate to severe TBI according to Glasgow Coma Scale, based on the lowest GCS score documented at scene of accident or in the emergency room immediately following the accident. Participants with TBI were in acute phase of recovery with time since injury (TSI) ranging from 12 to 89 days at the time of recruitment/data collection.

Participants selected did not have any of the following characteristics: history of multiple head injuries; pre-existing neurological, psychiatric, or developmental disorders; or, recent treatment for substance abuse. Participants also had to be free of visual field and upper extremity motor deficits, as these would interfere with their ability to complete the experimental tasks.

The experimental tasks required participants to view different visual displays on a computer screen. The visual displays consisted of either two or eight circles which were black line drawings against a white background. In the focused attention task, the screen displayed a spatial cue - an arrow pointing to a specific area of the screen. Then, the screen showed the target visual display of circles, each with a line intersecting it. Participants were instructed to search for a specific target - a circle without a line intersecting it - in the area of the screen to which the arrow had pointed. The divided attention task was similar, however, for that condition, the participants did not see a spatial cue before they were instructed to search for the target.

Participants were to press a button labeled “yes” if the target (a circle without a line intersecting it) was present in the display or press a button labeled “no” if it wasn’t present. Half of the visual displays required target-present “yes” responses and the other half were target-absent “no” responses. Participants’ rates of accuracy and reaction times (RTs) for correct responses were analyzed.

Results: What were the outcomes of the experimental measures? For the focused attention task, participants with TBI had similar rates of accuracy to controls regardless of display size (two or eight circles). Controls’ RTs were significantly faster than those of the participants with TBI. RTs were faster for the smaller display size (two circles) than for the larger display size (eight circles) for both groups. Participants with TBI had slower RTs for target-absent responses; the presence or absence of the target did not affect controls’ RTs.

For the divided attention task, controls again responded faster than participants with TBI overall. All participants were faster when the display included two circles and when the target was present. However, participants with TBI were more affected by the presence of added distractors (i.e., eight circles), particularly for the target-absent trials, than the controls. As with the focused attention task, accuracy rates were similar across controls and participants with TBI. 

These results suggest that selective attention abilities appear to be affected differently based on whether or not attention is first directed by the use of a spatial cue (i.e., an arrow directing them where to search). When the cue was used, participants with TBI were able to respond faster, suggesting that they were better able to ignore irrelevant information (i.e., distractors). The authors suggest that this may be due to decreased processing demands on an individual’s limited capacity attention resources when a specific directional cue is present. They also suggest that an underlying visuospatial impairment could also be a factor in the performance of participants with TBI on these tasks.

Clinical applications: What are the take home messages for me as an SLP? Deficits in selective attention can affect rehabilitation by increasing distractibility and reducing general cognitive capacity, as clients attempt to process potentially irrelevant information simultaneously with more relevant information. This study suggests that we may be able to assist adults with acute moderate to severe TBI by teaching them to use spatial cues to help direct/orient their attention to visual stimuli while being mindful of visual distractors.

Functional applications of this might include arranging items in a way that make them more efficient for the individual to find. For instance, if the goal is for the client to select and prepare his own bowl of cereal for breakfast every morning, it might be helpful to keep all of the items needed for this task in close proximity to one another. Perhaps the client or his family members could put cereal and a spoon in a bowl, along with the appropriate amount of milk in a cup on a specific shelf in the refrigerator together for the following day’s breakfast. Another potential application might be related to hygiene. Rather than having oral hygiene items in different places in the bathroom, a client might be better served by keeping her floss, toothbrush, toothpaste, and mouthwash in a basket together. This would prevent her having to look in a drawer, a cabinet, and beside the sink to gather the necessary items, and potentially becoming distracted along the way. Keeping in mind that clients in the acute recovery phase of TBI may have some relatively preserved attentional capacities, we may be able to capitalize on this to help them regain independence and decrease frustration in their daily lives.

Article 2: Wammes, J. D., Good, T. J., & Fernandes, M. A. (2017). Autobiographical and episodic memory deficits in mild traumatic brain injury. Brain and Cognition, 111, 112-126.

Background: Why was this study conducted? The authors of this article set out to learn more about the type and severity of memory difficulties experienced by adults who have sustained a mild traumatic brain injury (mTBI), sometimes referred to as concussion. While these individuals often report cognitive difficulties including confusion and memory problems in the first several months post-injury, the scientific literature relative to the presence of long-term memory deficits among individuals with mTBI is mixed, with some studies finding behavioral evidence of such impairments, and others not.

Studies have found evidence of physiological signs of mTBI as measured by a neuroimaging technique called diffusion tensor imaging (DTI). DTI studies have reported signs of diffuse axonal injury in individuals with mTBI. In addition, DTI studies have suggested that the “medial temporal lobe and the fornices (which have projections to and from bilateral hippocampi) are among the areas where white matter integrity is most compromised in mTBI” (p. 113). Damage in these specific white matter areas have been linked to impairments in attention and memory by some researchers. Given the apparent presence of physiological changes to the brain following mTBI, memory deficits could persist, though they may be subclinical in nature, based on the somewhat inconclusive behavioral evidence.

Many adults with mTBI report experiencing long-term memory problems as a result of their injuries, particularly in their memory for their own life events from day to day. However, the measures typically used to study memory in research, which include general neuropsychological batteries and experimental tasks that assess other types of memory, may not be valid measures of the specific type of memory that adults with mTBI report the most difficulty with - personal autobiographical memory. Personal autobiographical memory is a type of episodic memory. The authors of this study suggest that the disconnect between the type of memory difficulties reported and the measures often utilized in research could be a reason that the behavioral evidence has shown mixed results.

Also of interest to these researchers was the question of characterizing episodic and semantic memory function among adults with mTBI as they age. Memory in normal aging is marked by declines in performance on episodic memory tasks, while semantic memory is relatively preserved. This pattern is also observed among younger adults with a history of mTBI, suggesting that normal older adults and younger adults with mTBI might exhibit similar profiles with regard to memory function. This behavioral evidence seems to correspond with neuroimaging findings. DTI studies have shown similar white matter changes in these two populations. Evidence also suggests that older adults who have a history of mTBI perform worse on some types of memory tasks than older adults without a history of mTBI. The authors of this study wanted to explore whether older adults with normal cognitive aging and younger adults with mTBI have similar patterns of episodic and semantic memory function and whether having a mTBI as a young person might exacerbate the declines associated with normal cognitive aging. Specifically, the authors asked: What is the nature and severity of any lingering memory deficits experienced by individuals with a history of mTBI?

Method: Who participated in the study and what did they do?  A total of 81 participants were included in the study: 17 younger adults with mTBI, 32 younger adults without mTBI, 20 older adults with mTBI, 22 older adults without mTBI. For the purposes of this study, mTBI “was defined as any closed head injury that resulted from the head being hit, the head striking and object, or any acceleration/deceleration force that resulted in loss of consciousness (1 minute to 6 hours) or post traumatic amnesia (1 minute to 7 days)” (p. 115).

Because the aim of the study was to examine the long-term effects of of mTBI, participants were only included if their injury had occurred more than one year prior to the beginning of the study. Exclusionary criteria included the presence of comorbidities (i.e., mental illness) and reporting a history of multiple brain injuries with a range of severities. Each of the experimental groups (i.e., those with a history of mTBI) was age matched with the control groups, and all groups were also matched for years of education.

The participants completed several tests of general cognitive functioning, as well as three experimental tasks: free recall, semantic priming, and the modified Autobiographical Interview (AI) (from Levine et al, 2002). The semantic priming task will not be discussed here because it did not prove to be a very meaningful measure in terms of the research questions.

For the free recall task, participants were first shown 16 words, one word every 2 seconds. This was called the encoding phase. During the following time period, the retention period, participants completed a general cognitive test, the Trail Making Test. After that, they were asked to verbally recall as many of the 16 words as they could. The number of words recalled by each participant was recorded for analysis.

The modified AI task was an autobiographical memory task designed to elicit verbal accounts of four memories from the participants’ pasts. Each account was to be 30 seconds to 1 minute in length. These accounts were audiorecorded then transcribed and coded for episodic memory and semantic content. Two raters who were blinded to group membership coded the passages. Information describing a specific event with a specific place and time were coded as episodic memory details. Statements of facts or general knowledge were coded as semantic memory details.

Results: What were the outcomes of the experimental measures? Analyses of the general cognitive measures revealed that the older adults outperformed the younger adults on a measure of general semantic knowledge (the Mill Hill Vocabulary Scale). For the measure of attention, executive function and cognitive flexibility (the Trail Making Test), the younger participants were significantly faster at completing the task. No other significant differences were revealed for the general cognitive tests.

For the free recall task, the younger participants recalled significantly more words than the older adults and the participants with no history of mTBI recalled significantly more words than those with a history of mTBI.

For the autobiographical memory (modified AI) task, the younger participants with mTBI produced fewer details overall and fewer episodic memory details than age controls. No significant differences were found between the groups of older adults. However, older adults generated more semantic details than the younger adults. In fact, the younger and older groups had similar numbers of total details but exhibited opposite profiles within their stories: the older adults produced fewer episodic memory details and more semantic memory details, while the younger adults produced more episodic memory details and fewer semantic details. Overall, the fewest total details were given by the participants in the younger group with mTBI.

Additional analyses revealed that, even though some of the results of the experimental tasks did not reach statistical significance, a specific profile did emerge among individuals in both the older and younger mTBI groups. This profile was characterized by deficits in free recall of previously encoded information and production of fewer episodic details in the autobiographical memory task.

The authors concluded that these findings correspond to neuroimaging studies that have found decreased function in specific brain areas that form critical connections to the hippocampus. Furthermore, they concluded that the profile demonstrated by the participants in this study suggests relative preservation of semantic memory with specific deficits associated with episodic memory in mTBI. This pattern was also observed in older adults, corresponding with previous research and neuroimaging.

Clinical applications: What are the take home messages for me as an SLP? The results of this study suggest that individuals with a history of mTBI exhibit chronic memory deficits, specifically in episodic memory for autobiographical information and free recall of previously briefly encoded information. Furthermore, these results found a profile of performance suggestive of a better command of and heavier reliance on semantic knowledge in older adults, regardless of mTBI status. Overall, the study supports the role of SLP services for individuals dealing with chronic memory deficits following mTBI, and helps illustrate the potential need for skilled SLP services for individuals with mTBI in the longer-term. Specifically, individuals with mTBI may benefit from SLP services to assess the negative effects of their memory deficits on activities of daily living, design effective compensatory strategies, and instruct individuals and their caregivers on these strategies to help them improve functional outcomes. SLPs should consider developing and teaching compensatory strategies for autobiographical episodic memory when working with individuals in the acute stage of mTBI. These strategies might include internal and external memory aids.  Internal memory aids include techniques like semantic associations or visualization to remember details. Examples of external memory aids are physical objects like lists, calendars, or portable/pocket voice recorders.

Assessment of Attention and Memory Skills in Individuals with TBI 

Article 3: Brown, J., & Hux, K. (2017). Ecologically valid assessment of prospective memory for task planning and execution by adults with acquired brain injury. American Journal of Speech-Language Pathology, 26, 819-831. 

Background: Why was this study conducted? Planning and executing future tasks are crucial skills for successful independent living. Two cognitive skills in particular are required to engage in planning and execution of future tasks - planning and prospective memory. Planning is considered an executive function and involves the following of steps to engage in goal-oriented behavior to accomplish a task. Furthermore, planning is a complex construct that requires the integration of several other cognitive skills including making predictions, self-regulation, self-monitoring, and memory. Not surprisingly, individuals with acquired brain injury (ABI) often have significant difficulty with planning. In order to provide more effective services to individuals with ABI, we need to know more about where and how the breakdowns occur within the various cognitive processes required to support successful planning.

Like planning, adequate prospective memory is required to engage successfully in a number of daily activities. Prospective memory involves forming the intention to carry out an action at a later time or date, i.e., “I need to remember to stop by the post office to drop off that package after work”. Prospective memory can be especially difficult for individuals with ABI because it requires one to be proactive in performing a memory search to remember what it is that they are supposed to do at a given time. This is particularly challenging for individuals with ABI because they often have difficulty with initiating actions. This would apply to a number of tasks required for living independently, such as taking medications correctly and paying bills on time. For this reason, deficits in prospective memory may have a significant and direct effect on an individual’s prognosis for returning to living independently in the community.

The authors of this study suggest that more information is needed regarding the nature and severity of prospective memory deficits among adults with ABI. They argue that typical neuropsychological assessment batteries are not designed to tap into planning, prospective memory, and task execution. In fact, research cited by these authors suggests that functional outcomes for individuals with ABI are not correlated with formal tests of executive functioning - in other words, these formal tests are not necessarily ecologically valid as they do not measure deficits as they are experienced by these individuals in their day to day activities. The purpose of this study was to explore the utility of an assessment protocol specifically developed to test planning, prospective memory, and task execution by adults with chronic, severe ABI in an ecologically valid manner.

Method: Who participated in the study and what did they do? Participants included seven men and two women with chronic, severe ABI. For the purposes of this study, ABI was defined as “an injury resulting in diffuse brain damage stemming from a traumatic event, an anoxic episode or an infection” (p. 821). Participants were between 6 and 38 years post injury, and ranged in age from 29 to 54 years, and were residents of assisted-living apartments in a transitional rehabilitation facility. They were identified by facility staff as having “persistent cognitive deficits interfering with sustained, gainful employment and independent living” (p. 821). Participants were required to be able to read at a 6th grade level or higher, to have oral communication skills adequate for casual conversation, and to be able to write down novel information. A control group of seven men and two women with no history of brain injury or other neurological impairment was matched to the group of participants with ABI on age and years of education.

The experimental task consisted of two phases. Phase 1, Prospective Task Planning, required participants to read a list of instructions for completing eight tasks over 10 days. Participants were provided with a set of rules, which stipulated several requirements including that they were allowed to complete the tasks in any order over the subsequent 10 days, but they were not permitted to complete more than one task per day. The participants were to develop a plan for completing the tasks within the stated parameters, and to write the plan on the provided planning documents/calendars. While the participants were engaged in this planning, the researchers recorded qualitative descriptions of their behaviors. The amount of time from the beginning of the planning activity till the end was measured, as was the number of important details present in the written planning documents.

Phase 2, Prospective Task Execution, required the participants to provide the researchers with specific evidence (i.e., a voicemail or email) of the completion of each of the eight tasks they had planned for in Phase 1. For Phase 2, the researchers measured the number of attempted and accurately completed tasks, number of rules violated, and frequency of rule violation.

Results: What were the outcomes of the experimental measures? Participants with ABI spent an average of over 18 minutes on the planning task, while controls spent an average of just under 14 minutes. This difference was not statistically significant, which might have been related to the great deal of variability in planning times among participants with ABI, ranging from just under 4 minutes to 37 minutes. The range for controls was less variable, just under 9 minutes to just under 22 minutes.

Participants with ABI wrote down fewer information units during the planning process than controls but again, this difference was not statistically significant. Analyses revealed a significant relationship between time spent planning and number of written details for the participants with ABI, meaning that the longer the time spent on the planning task, the more details recorded, and the less time spent, the fewer were recorded. The same relationship was found for the controls, but it was not statistically significant in that group.

Qualitative observations of the participants revealed differences between the two groups. The researchers noted that most of the participants in the control group used effective strategies during the planning task, including utilizing the calendar. None of the participants with ABI utilized the calendar. Participants with ABI exhibited “frustration and confusion” during the planning process, while similar behaviors and comments were not observed among controls.

With regard to completion of the eight tasks that the participants were instructed to plan for and execute, participants with ABI completed significantly fewer tasks than those without ABI. In addition, participants with ABI violated more rules and violated them more frequently than those without ABI.

The authors discuss potential reasons for the differences between participants with ABI and those without. These include a variety of difficulties exhibited by adults with ABI, such as: deficits in task initiation, inadequate information encoded during the planning process, motivation, and the 10-day timeframe the participants had in which to complete the tasks (especially because participants did not have access to external memory aids). Ultimately, results suggest that, while none of the participants completed the experimental protocol perfectly, those with ABI performed significantly worse than the control group. The researchers point out that the protocol utilized in this study is not an absolute reflection of planning and prospective memory functions in the real world, but they argue that the assessment procedures they piloted here represent a promising ecologically valid tool.

Clinical applications: What are the take home messages for me as an SLP? While the results of this study probably do not come as a surprise to SLPs, especially those who have worked closely with adults with brain injury, they do provide some interesting take home messages. The findings suggest that significant variability exists among individuals in this clinical population with respect to time required to complete certain tasks. Although the mean time spent planning was 18 minutes, the data confirm that some participants with ABI spent much less time than that, while others took twice as long as the average. Further, the data suggest that participants who spent less time in the planning phase wrote down less detailed information to assist them in executing the prospective tasks. Compounding the lack of information these participants included in their planning documents was the observation that none of them utilized one of the most helpful documents at their disposal - a calendar.

These findings suggest that adults with severe chronic ABI might benefit from strategy instruction that focuses on spending more time planning prospective tasks, making note of key details associated with these tasks, and effectively using planning documents like calendars. As with Article 2, this study seems to support the need for long-term SLP services among individuals with severe brain injury to assist in developing and implementing effective cognitive communicative strategies. The study also highlights the importance of using ecologically valid assessments to determine functional individualized treatment programs for adults with brain injury.

Final Thoughts

The studies highlighted here focus on characterizing and assessing various attention and memory skills among adults with mild to severe brain injuries in acute and chronic stages. Overall, this research provides evidence for the medical necessity of SLP services from the acute phase of TBI through the longer-term, chronic stages of TBI. The findings illustrate the need for SLP services to provide ecologically valid assessment in order to determine cognitive-communicative strengths and weaknesses and to develop comprehensive functional individualized treatment plans that include the development and implementation of effective compensatory strategies. Though two of the three articles reviewed here come from journals outside of the discipline of SLP and do not refer to SLP services specifically, they clearly demonstrate the need for our services in this population.

None of the studies reviewed here included individuals with blast-related brain injuries, which are frequently the cause of TBI among military personnel/veterans. Research suggests that blast-related injuries among military personnel may present differently from non-blast related injuries in terms of symptoms and recovery (Chapman & Diaz-Arrastia, 2014), so we must keep this in mind as we work with adults with TBI from different backgrounds and different types of injuries.


april garrity

April Garrity, PhD, CCC-SLP

April Garrity, PhD, CCC-SLP is associate professor of communication sciences and disorders in the Department of Rehabilitation Sciences at Georgia Southern University’s Armstrong Campus. Her teaching and research interests include language acquisition and impairment across the lifespan and clinical populations, linguistic variation, and the effects of various pedagogical approaches on learning. She also maintains an active clinical practice with adults.



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